A Gap Metric Based Nonlinearity Measure for Chemical Processes

Almost all chemical processes are inherently nonlinear, whereas not all of them require nonlinear control. This leads to an interesting question "when is a linear controller adequate and when is a nonlinear controller warranted?" This paper proposes a nonlinearity measure based on gap metric to quantify the nonlinearity degree of chemical processes, aiming to answer such a question. The proposed measure is of great use to analysis and synthesis of nonlinear systems. A benchmark continuous stirred tank reactor (CSTR) process and a double effect evaporator (DEE) system are presented to illustrate the effectiveness to the proposed nonlinearity measure.